Why is my efficiency declining?

[jldc]

I have been brewing AG for about a year, 20 batches or so. I use a double-batch sparge, 10 gallon cooler system. I started out getting 80-82%, but that has steadily declined to 68-70%. Nothing about my process has changed. I'm hitting my temps well and using the same hydrometer.

My thoughts:
Crush: I have a barley crusher. Is it possible that the gap is slowly slipping and getting wider? I am going to pick up some feeler gauges and check.

Volumes/Boil-Off: After I fill my carboys, I have varying volumes remaining in the brewpot. In other words, boil-off varies. I just eyeball the kettle to keep it at a "rolling boil." I'm going to start accurately measuring the remaining volume in the kettle to more accurately figure my efficiency.

Any other thoughts on where I could be loosing efficiency. I should add that I don't really care what number I hit (within reason), I want to hit that number reliably so I can brew exactly the beer I want to brew.

 

[Surly]

Have you checked your thermometers of late? If they are off, you may not be converting what you used to.

 

[gturner6ppc]

Since you said it has been steadily declining, my guess is it's from wear or loosening on your crusher.

 

[zanemoseley]

I noticed a big jump after going from floating thermometers to digital, perhaps your thermometers are not as accurate as they were. Crush is always another variable.

 

[powderbock]

Check your thermometer. I noticed a similar problem, was missing my FG by quite a bit, happened to check my probe thermometer in an ice bath when cooling my yeast starter, it was low by 4 degrees.

 

[The Pol]

Conversion or lauter eff. is declining?

 

[wrestler63]

Since you said it has been steadily declining, my guess is it's from wear or loosening on your crusher.

agreed........new crusher needs attention to keep your crush accurate

 

[david_42]

+1 on checking the crusher. This has the biggest impact and is the most likely cause of a steadily changing problem. It's not unusual for a new machine to settle in gradually and need to be adjusted.

 

[pjj2ba]

Another vote for the crusher. I have an adjustable Crankenstein and after a batch with low efficiency, I checked my gap and found the rollers were not parallel anymore. I readjusted the rollers and my efficiency went back up.

 

[SpanishCastleAle]

Another vote for the crusher. I have an adjustable Crankenstein and after a batch with low efficiency, I checked my gap and found the rollers were not parallel anymore. I readjusted the rollers and my efficiency went back up.

Hate to pile on but this exact same thing happened to me with my Barley Crusher.

 

[jldc]

Have you checked your thermometers of late? If they are off, you may not be converting what you used to.

I have two thermapens and I always check them against each other at the beginning of the brew and against boiling (while I watch for the hot break). I don't think this is the issue.

My money is on the crusher, too. It has been a steady decline and not sudden drop.

 

[jldc]

An update: Adjusted the crush to 0.036 and my efficiency was 84% today.

 

[david_42]

Great, thanks for the update. Always good to know what the resolution is.